Q. Expain different control function categories,And also discuss that how they help in signalling and control.

Ans:

In some switching systems, Control subsystem may be an integral part of switching network itself. Such system are called direct control switching systems. Those systems in which control subsystem is outside switching network are called common control switching system. Strowger exchanges are generally direct control systems, whereas crossbar and electronic exchanges are common control system. All stored program control systems are common control systems. Common control is also called indirect control or register control.